Based on our previous studies and work reported by others we propose the existence in mammalian cells of at least two distinct receptors for E prostaglandins linked to adenylate cyclase. The first objective of the research proposed is to test this hypothesis. Thus, we intend to conduct a pharmacological characterization of the response to prostaglandins of a variety of cells in culture and of human and rat adipocytes, platelets and lymphocytes as well as in frog and turkey erythrocytes. The response measured will be the formation of cyclic AMP in intact cells using methods previously established in this laboratory. Once the classes of PGE receptors are delineated in terms of structure-activity relationships for both agonists and antagonists we will conduct a comparative analysis of the factors that influence the response of the different receptor-cyclase systems to prostaglandins. The following specific questions will be addressed experimentally: (1) Do non-steroidal anti-inflammatory agents which inhibit the interaction of PGE1 with one class of PGE-receptor, inhibit the interaction of PGE's with other classes? (2) Do all classes of PGE-receptor exhibit tachyphylaxis to continued exposure to PGE? What is the mechanism(s) by which loss of response occurs? (3) Do Glucocorticoids, which enhance the response of certain cells to PGE1, modify the PGE-receptor adenylate cyclase system? What is the mmchanism underlying this effect? (4) Does cholera toxin, which markedly enhances the effectiveness of PGE1 upon interaction with one class of PGE-receptor, have the same effect in cells with different PGE-receptors? What is the molecular basis for this effect of cholera toxin? (5) Is the endogenous synthesis of prostaglandins, endoperoxides and thromboxanes linked in any manner to the response of the cells to PGE's? (6) How do the properties of different classes of PGE-receptor-linked adenylate cyclases compare when examined in membrane preparations? The identification and characterization of different classes of adenylate cyclase-linked receptors for E prostaglandins should provide the basis for a more coherent interpretation of the effects of prostaglandins on physiological function.